The invention relates to a speed-adaptive vibration damper for a shaft rotating around an axis, which includes a hub part, on which are arranged a number of peripherally adjacent inertial masses that are movable along curved paths. The masses increasingly approach the axis in the peripheral direction on both sides so that, when rotational vibrations set in, a change occurs in the distance between the inertial masses and the axis.
Such a speed-adaptive vibration damper is known from German Patent B 196 04 160, which provides vibration damping, regardless of the instantaneous rotation speed of the rotating shaft, if a rotational vibration is superimposed on the rotational motion. The natural frequency of the damper changes in proportion to the rotation speed of the shaft and allows the vibrations, which are also proportional to the speed, to be damped. In the case of an internal combustion engine, the excitation of the ignition frequency is of the greatest amplitude and results in non-uniform rotation of the crankshaft, which is attenuated by the speed-adaptive damper.
The object of the present invention is to improve on a vibration damper of the type noted above so that an improved damping effect is achieved without negatively affecting the damping effect over a broad frequency range if the rotation vibrations superimposed on the rotary motion are of a very small amplitude.
This object is achieved in a speed-adaptive speed-adaptive vibration damper for a shaft having a hub part, on which are a number of peripherally adjacent inertial masses that are movable along curved paths that increasingly approach the axis of rotation on both sides. Consequently, when rotational vibrations set in, a change occurs in the distance of the inertial masses from the axis.
In the vibration damper according to the present invention, at least one relatively twistable inertial ring is also elastically mounted on the hub part. The damping effect of the elastically mounted inertial ring is latently present even when rotational vibrations of very small amplitudes superimposed on a rotary motion set in.
The inertial ring may surround the hub part in the radial direction; it may be advantageous to arrange the inertial ring radially outside or inside the cylindrical surface delimiting the hub part. The elastic cushion that is used may be made of an elastomeric material, for example, rubber, and, it may connect the inertial ring and the hub part onto which it is directly vulcanized. The inertial ring may also be axially adjacent to one boundary face of the hub part. The radial diameter of the vibration damper can then be reduced accordingly without impairing effectiveness. Effectiveness over a broad range can be achieved by elastically mounting a plurality of inertial rings having different resonance frequencies on the hub part.
The hub part and/or the inertial ring may include at least one belt pulley, which may be an integral part of the hub part and/or of the inertial ring.
According to an advantageous embodiment, the hub part encloses an annular chamber, where the inertial masses and/or the inertial ring are accommodated. The effect of environmental influences on the inertial masses and/or the inertial ring is thus reduced, which may substantially contribute to an increase in service life and/or reliability.
It has proven to be advantageous for improved weight/performance ratio that the hub part be designed to be as lightweight as possible and be made, at least in part, of sheet metal. The hub part may then include a first partial hub with a chamber that is open in the axial direction where the inertial masses and/or the inertial ring are introduced, and is closed by a second partial hub in the area of its axial opening. The first and second partial hubs may be connected by at least one bead, which makes it easier to achieve very low production costs while ensuring excellent dimensional stability and reliability.
One preferred application of the speed-adaptive vibration damper is its arrangement on the front or rear end of the crankshaft of cylinder engines, in particular of internal combustion engines. The damping effect achieved in this case refers to the unevenness of rotation, rotational vibrations and bending vibrations that are superimposed on the rotation motion.
The invention permits the control of vibrations of great and small amplitudes in different frequency ranges, but also of bending vibrations that are superimposed on the rotation motion and cause concentric relative displacements of the vibration damper.